A cataract is a clouding of the eye's natural lens, the structure that sits behind the iris and helps focus light onto the retina. Over time, proteins in the lens break down and clump together, causing it to become cloudy, yellowed, or opaque. Light can no longer pass through clearly, leading to blurred vision, glare and halos around lights, faded colors, and difficulty seeing at night.
Cataracts develop gradually, most often as a natural part of aging, though they can also be influenced by prolonged UV exposure, certain medications (such as long-term steroid use), diabetes, previous eye injury or surgery, and family history. Nearly everyone will develop some degree of cataract if they live long enough — it's one of the most common eye conditions we treat, and also one of the most treatable.
There is no eye drop, medication, or exercise that reverses a cataract. Surgery is the only effective treatment, but the good news is that modern cataract surgery is one of the safest, most refined procedures in all of medicine, with a very high rate of success and patient satisfaction.